Background
Prehospital anaesthesia is a challenging procedure, and the outcome depends on the quality of the process. Hospital-acquired anaesthesia experience does not necessarily translate to high performance in the prehospital setting. We aimed to assess the quality and practice patterns in prehospital anaesthesia related to cumulative experience amongst new prehospital critical care physicians. In this study, we aimed to evaluate whether quality indicators for prehospital anaesthesia and related mortality improve as new prehospital critical care physicians become more experienced with this intervention.

Methods
We conducted a registry-based observational study including all patients who underwent anaesthesia and airway management by physicians who started working in the national HEMS between January 2013 and August 2019. Patients were grouped and compared based on the provider’s cumulative case volume at the time of the mission: 1–10, 11–20, 21–40, 41–80 and>80 cases. The association between cumulative experience and 30-day mortality was assessed using multivariate logistic regression analysis. Secondary outcomes included frst-pass intubation success, post-intubation hypoxia and hypotension, the combined use of a neuromuscular blocking agent and anaesthetic, onscene time, mechanical ventilation usage, and rates of normocapnia, hypoxia, and hypotension at handover.

Results
1,638 patients (median age 59, 64% male) were treated by 32 physicians. Median on-scene time decreased with increasing experience from 33 (interquartile range [IQR] 23–44) to 28 (IQR 19–38) minutes, P=0.03. Higher experience was associated with increased use of mechanical ventilation (P<0.001) and a combination of neuromuscular blocking agents and anaesthetics (P=0.03). Other secondary outcomes did not show a statistically signifcant diference between the groups. Crude mortality decreased from 38 to 26% in the lowest to highest experience groups. In the multivariate logistic regression analysis, the same trend was still seen with the odds ratio of the highest experience group for 30-day mortality 0.59 (95% CI 0.38–0.94, lowest experience group as a reference).

Conclusions
In a prehospital critical care service, outcomes improve after a high number of prehospital cases, even when physicians with a solid foundation in in-hospital anaesthesia are employed. Limiting physician turnover may improve the quality of care.